A college lab germ exposure scare sent 32 people onto precautionary antibiotics after a microbiology class appeared to identify its unknown sample as Neisseria meningitidis, according to a report in the CDC’s Morbidity and Mortality Weekly Report. State laboratory testing later found the class had handled a nonpathogenic relative instead, which is the sort of relief that still leaves a paperwork crater.
The incident involved 33 people, including students, instructors and laboratory workers, who were considered exposed during a teaching exercise. The class had been given an unknown bacterium to identify using biochemical tests and morphology. The intended organism was Plesiomonas shigelloides, a common environmental bacterium that can cause diarrhea but is not treated like a high-risk teaching-lab pathogen.
The result was stranger. Every student identified the organism as N. meningitidis, a bacterium that can cause meningitis and bloodstream infections. When instructors reviewed the work, they found the class’s test results matched that conclusion: a gram-negative diplococcus that was oxidase-positive and catalase-positive, with carbohydrate fermentation results consistent with N. meningitidis.
What happened in the college lab germ exposure scare?
University officials found a vial labeled N. meningitidis in the same stockroom freezer where the intended teaching organism was stored, according to the CDC report. Because N. meningitidis can spread through aerosols in a lab, it is supposed to be handled with tighter controls, including respiratory protection and a biosafety cabinet. The people in the class had used gloves and lab coats.
State public health officials were brought in to assess risk, test samples and advise the university. They recommended a 10-day course of post-exposure prophylactic antibiotics for the 33 people considered exposed. Thirty-two started the regimen. Officials also noted that 15 of the 33 people, or 45 percent, had previously received at least one meningococcal vaccine.
Two people later sought emergency care for headaches and received lumbar punctures to check for possible N. meningitidis infection. The report describes the symptoms as mild. No dangerous exposure was confirmed.
How did the bacterium get misidentified?
Several days after the lab exercise, the state public health laboratory analyzed two samples using mass spectrometry and whole-genome sequencing. Those methods identified the organism as Neisseria sicca, a nonpathogenic relative of N. meningitidis.
The state lab then repeated the carbohydrate fermentation tests the students had used. It got the same misleading pattern. Investigators concluded this particular N. sicca isolate had atypical fermentation behavior, which likely explains both the class’s result and the mislabeled stockroom vial.
N. meningitidis is treated seriously because it can invade the membranes around the brain and spinal cord or enter the bloodstream, both of which can become life-threatening. N. sicca, by contrast, is not considered a pathogen in this context, but the lab tests used in the class made it look like the wrong cousin.
State and federal health officials later reviewed how the university stored and tracked biological materials. They found weak inventory controls for identifying, labeling, storing and separating samples by handling requirements and containment conditions. They also cited limited supervision of stockroom employees, problems with personal protective equipment availability and use, and poor documentation of sample inventory, disposition and chain of custody.
According to the CDC report, the findings led the university to revise its procedures and protocols. The people involved avoided infection, but the episode shows how a mislabeled vial and a quirky organism can turn a teaching exercise into an avoidable public health response.
This story draws on original reporting from Ars Technica.
